fix(memory): add thread-safe singleton initialization

- Add threading.Lock with double-check locking to ScopeManager
- Add asyncio.Lock with double-check locking to MemoryReflection
- Make reset_memory_metrics async with proper locking
- Update test fixtures to handle async reset functions

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/services/memory/metrics/collector.py

@@ -499,10 +499,11 @@ async def get_memory_metrics() -> MemoryMetrics:
         return _metrics
 
 
-def reset_memory_metrics() -> None:
+async def reset_memory_metrics() -> None:
     """Reset the singleton instance (for testing)."""
     global _metrics
-    _metrics = None
+    async with _lock:
+        _metrics = None
 
 
 # Convenience functions

backend/app/services/memory/reflection/service.py

@@ -7,6 +7,7 @@ Implements pattern detection, success/failure analysis, anomaly detection,
 and insight generation.
 """
 
+import asyncio
 import logging
 import statistics
 from collections import Counter, defaultdict
@@ -1425,8 +1426,9 @@ class MemoryReflection:
         )
 
 
-# Singleton instance
+# Singleton instance with async-safe initialization
 _memory_reflection: MemoryReflection | None = None
+_reflection_lock = asyncio.Lock()
 
 
 async def get_memory_reflection(
@@ -1434,7 +1436,7 @@ async def get_memory_reflection(
     config: ReflectionConfig | None = None,
 ) -> MemoryReflection:
     """
-    Get or create the memory reflection service.
+    Get or create the memory reflection service (async-safe).
 
     Args:
         session: Database session
@@ -1445,11 +1447,15 @@ async def get_memory_reflection(
     """
     global _memory_reflection
     if _memory_reflection is None:
-        _memory_reflection = MemoryReflection(session=session, config=config)
+        async with _reflection_lock:
+            # Double-check locking pattern
+            if _memory_reflection is None:
+                _memory_reflection = MemoryReflection(session=session, config=config)
     return _memory_reflection
 
 
-def reset_memory_reflection() -> None:
+async def reset_memory_reflection() -> None:
-    """Reset the memory reflection singleton."""
+    """Reset the memory reflection singleton (async-safe)."""
     global _memory_reflection
-    _memory_reflection = None
+    async with _reflection_lock:
+        _memory_reflection = None

backend/app/services/memory/scoping/scope.py

@@ -7,6 +7,7 @@ Global -> Project -> Agent Type -> Agent Instance -> Session
 """
 
 import logging
+import threading
 from dataclasses import dataclass, field
 from typing import Any, ClassVar
 from uuid import UUID
@@ -448,13 +449,24 @@ class ScopeManager:
         return False
 
 
-# Singleton manager instance
+# Singleton manager instance with thread-safe initialization
 _manager: ScopeManager | None = None
+_manager_lock = threading.Lock()
 
 
 def get_scope_manager() -> ScopeManager:
-    """Get the singleton scope manager instance."""
+    """Get the singleton scope manager instance (thread-safe)."""
     global _manager
     if _manager is None:
-        _manager = ScopeManager()
+        with _manager_lock:
+            # Double-check locking pattern
+            if _manager is None:
+                _manager = ScopeManager()
     return _manager
+
+
+def reset_scope_manager() -> None:
+    """Reset the scope manager singleton (for testing)."""
+    global _manager
+    with _manager_lock:
+        _manager = None

backend/tests/unit/services/memory/metrics/test_collector.py

@@ -21,9 +21,9 @@ def metrics() -> MemoryMetrics:
 
 
 @pytest.fixture(autouse=True)
-def reset_singleton() -> None:
+async def reset_singleton() -> None:
     """Reset singleton before each test."""
-    reset_memory_metrics()
+    await reset_memory_metrics()
 
 
 class TestMemoryMetrics:
@@ -333,7 +333,7 @@ class TestSingleton:
         metrics1 = await get_memory_metrics()
         await metrics1.inc_operations("get", "working", None, True)
 
-        reset_memory_metrics()
+        await reset_memory_metrics()
 
         metrics2 = await get_memory_metrics()
         summary = await metrics2.get_summary()

backend/tests/unit/services/memory/reflection/test_service.py

@@ -59,9 +59,9 @@ def create_mock_episode(
 
 
 @pytest.fixture(autouse=True)
-def reset_singleton() -> None:
+async def reset_singleton() -> None:
     """Reset singleton before each test."""
-    reset_memory_reflection()
+    await reset_memory_reflection()
 
 
 @pytest.fixture
@@ -757,7 +757,7 @@ class TestSingleton:
     ) -> None:
         """Should create new instance after reset."""
         r1 = await get_memory_reflection(mock_session)
-        reset_memory_reflection()
+        await reset_memory_reflection()
         r2 = await get_memory_reflection(mock_session)
 
         assert r1 is not r2